Clarify receipt-first landing proof

[sarthakagrawal927]

Summary

• show a truthful illustrative packet/fill/submit receipt in the hero
• route “See Receipts” to the actual receipt section
• add visible focus, reduced-motion handling, and 44px header targets
• refresh 390/768/1440 evidence and design receipt

Validation

• pnpm --dir landing-astro build
• commit-hook Biome check (287 files)
• Fleet design-review checker: 36/40 critique, 19/20 audit
• browser review at 390, 768, and 1440: no overflow or application console errors
• jq empty .fleet/design-review.json
• git diff --check

The isolated preview still requests a missing favicon; that existing 404 is recorded in the receipt and is not an application error.